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Inside System Storage -- by Tony Pearson

Tony Pearson is a Master Inventor and Senior IT Specialist for the IBM System Storage product line at the
IBM Executive Briefing Center in Tucson Arizona, and featured contributor
to IBM's developerWorks. In 2011, Tony celebrated his 25th year anniversary with IBM Storage on the same day as the IBM's Centennial. He is
author of the Inside System Storage series of books. This blog is for the open exchange of ideas relating to storage and storage networking hardware, software and services. You can also follow him on Twitter @az990tony.
(Short URL for this blog: ibm.co/Pearson
)

In case you missed it, IBMunveiled a new digital video surveillance service yesterday. This "marks an important shift in the industry's approach to security, applying advanced analytics to video data and signaling the ability to converge physical and information technology (IT) security."

The IBM Smart Surveillance Solution is designed to provide the unique capability to carry out efficient data analysis of video sequences either in real time or from recordings. These recordings can be on disk or tape storage.

The problem with today's existing "analog" surveillance is that the analog cameras record onto traditional VHS tapes, and these are rotated through, re-written after a few hours or days. To review tapes often involves human intervention, and must be done before the VHS tapes are re-used. Many shoplifters, thieves, and other law-breakers take a chance that their actions will not be caught on tape, or that they will be long gone by the time the video is analyzed.

The IBM Smart Surveillance Solution can provide a number of advantages over traditional video solutions, including:

Real-time alerts that can help anticipate incidents by identifying suspicious behaviors.

Forensic capabilities are enhanced by utilizing unique indexing and attribute-based search of video events to classify objects into categories such as people and cars.

Situational awareness of the location, identity and activity of objects in a monitored space including license plate recognition and face capture.

With real-time analytics capabilities, the new DVS service can open up a wide array of new applications that go far beyond the traditional security aspects of surveillance systems. Early adopter industries in this rapidly evolving market include retail, public sector and financial services. The retail industry estimates nearly $50 billion is lost annually to fraud, theft and administrative errors.

Once in digital format, video surveillance can be sent further, processed quicker, and stored for longer periods of time, than traditional media makes practical today.

Several of my IBM colleagues will be attending the "Virtual Worlds 2007" conference today and tomorrow. This conference sold out so quickly that they have already scheduled a second one for October. The focus is on 3-D internet technologies likeSecond Life. Attendance is expected at over 600 people.

IBM is investing heavily in this new concept of v-business. Last year, I was one of only 325 IBMers on Second Life. Now, according to this Better than Life blog entry from Grady Booch, IBM Fellow, the number is over 4000!

Of course, the challenge for IBM, and others, is learning to market in virtual worlds. Already, my team is in-world, and we meet several times a week. Using Second Life is quickly becoming an essential business skill, like participating in conference calls, or responding to instant messages.

What does meeting in-world entail?

Scheduling a time and a place

Finding a time that people can meet is no different than scheduling a audio or video conference call. In general, you don't have to worry about travel, but you do have to be actively somewhere connected to everyone else.

Finding a place involves actually determining the island, region and coordinates to hold the meeting. You need to find a place with enough seating. You don't have to worry about daylight, each person can control how much or little sunlight shows up on their screen. You do have to make sure you pick a spot that nobody else plans to use at that same time. Just like scheduling conference rooms at the site or hotel, we have to schedule rooms in advance.

To avoid this hassle, I have created the "pocket conference room". This is a single object that I can "rez" onto the ground, from my inventory, with 40 chairs, a PowerPoint presentation screen, a podium for a speaker to stand behind, and stools for speakers to sit on if they are next on the agenda. Now, I can hold impromptu meetings in any sandbox, grassy knoll, or the roof top of a building.

Ground Rules

As with any other meeting, you need some basic ground rules. I am not talking the usual "no shooting, no gambling, no selling" rules that you see everywhere in Second Life. Instead, rules like an avatar must stand up before speaking. Anyone with a question must first "raise their hand" and get recognized by the chair. These ground rules can be as formal as Robert's Rules of Order or more casual, depending on who is participating.

Presentation

It costs 10 Linden Dollars (L$) per PAGE to upload a PowerPoint presentation. This has the immediate benefit of having everyone spend more time and effort on their presentation, trying to cut down the number of charts, and focus more on what they are going to say.

Public Speaking Skills

It is amazing. People who are too scared to speak in front of an audience in Real Life have no problem having their avatar stand in front of other avatars in Second Life. This has greatly broadened the pool of speakers to tap into.Are you a woman with a husky masculine voice? Are you a man with a high-pitched feminine voice? Now, you can create an avatar that matches your voice.

The Audience

This turns out to be the biggest challenge. In Real Life, organizing a face-to-face meeting involves time and effort making sure the venue has everything you need, a platform, a podium, good Audio/Video system, etc. All people have to do is show up, sit in a chair and listen.

In Second Life, however, the aspects of venue are all covered, but getting people to show up is another story. People have to sign up for Second Life account, create an avatar, wear appropriate virtual clothing, figure out how to teleport near the venue, walk or fly the difference to get to the exact building and room, master the sitting-in-a-chair and hold-coffee-and-sip-occasionally process, and pay attention.

Perhaps the best part of Second Life is that if you are not paying attention, your avatar noticeably falls asleep, into a hunched-over position, what is called "afk" (short for Away From Keyboard). On the other hand, if you do need to step away from your desk, you can put your avatar in "afk" mode immediately, tell everyone why and perhaps when you'll be back, and then re-activate when you return. This is one of the best improvements over regular audio conference calls.

I suspect the need for having places in Second Life to hold meetings will become more and more in demand.At a time when real-estate sales in the US is slowing down, Coldwell Banker's Second Life efforts are ramping up. I am not making this up. Coldwell Banker is one of the nation's largest real estate brokerage firms. They are trying to bring the same "adult supervision" to virtual real-estate transactions, offering to help people buy and rent properties in Second Life.

Our site manager, Terri Mitchell, did a recap of all our recent awards and accomplishments.Of the nine Design Innovation awards won by IBM this year at the CeBIT conference, eight were for IBM System Storage products!

The IBM System Storage EXP3000: an entry-level data storage server that is optimized for cost-sensitive and space-limited environments and employs a user-centered design that enables ease of use and simple tool-less installation and removal of all components.

The IBM System Storage N5000 Series: a modular disk storage system designed to address the entire spectrum of data availability challenges while offering value in price and scalability. Built-in enterprise serviceability and manageability features support efforts to increasereliability and simplify storage infrastructure and maintenance.

The IBM System Storage N3700: a filer that integrates storage and storage processing into a single unit, facilitating affordable network deployments.

The IBM System Storage DS4700: a NEBS-compliant disk storage server designed to address requirements for companies in the telecommunications industry, as well as other segments, such as oil and gas, meeting standardsfor electromagnetic compatibility, thermal robustness, earthquake and office vibration resistance, and provides protection for the product components from airborne contaminants.

The IBM System Storage EXP810: a data storage expansion unit capable of 4.8 Terabytes of physical storage, with a user-centered and tool-less design featuring redundant power, cooling, and disk modules for ease of use and simple serviceability.

The IBM System Storage TS3400: an affordable, space-friendly tape library for users in remote locations that supports enterprise-class technology and encryption capabilities.

A representative from Tucson's Brewster Center presented Terri an award, thanking IBM for its strong support for the community through various charity initiatives.

The final speaker was a new IBM client, Tony Casella, the IT Director of the town of Marana. Recently, the town of Marana selected IBM products made big news. Arizona is the fastest growing state in the USA, and the town of Marana, just north of Tucson, is one of the fastest growing communities in Arizona. The town is growing so large that it will soon spill over from Pima into Pinal county, and will be the first town in Arizona authorized to span county boundaries.

The Magic Quadrant is copyrighted concept by Gartner, representing a two-by-two grid that ranks various offerings from different vendors. Ideally, vendors want their products in the upper right "Leaders" quadrant. Yahoo Finance reports:

According to Gartner, Inc., "Leaders have the highest combined measures of an ability to execute and a completeness of vision. They have the most comprehensive and scalable products. They have a proven track record of financial performance and an established market presence. In terms of vision, they are perceived as thought leaders, having well-articulated plans for ease of use, how to address scalability and product breadth. For vendors to have long-term success, they must plan to address the expanded market requirements for change management and root-cause and performance analysis. Leaders must not only deliver to the current market requirements, which continue to change, but they also need to anticipate and deliver on future requirements. A cornerstone for leaders is the ability to articulate how these requirements will be addressed as part of their vision for resource management. As a group, leaders can be considered a part of most new purchase proposals, and they have high success rates in winning new business."

IBM TotalStorage Productivity Center is a strategic part of IBM Service Management, and a foundational component of the IBM Systems Director family. IBM is making a concerted effort across servers, networks, software and storage to help manage the IT infrastructure in a coordinated way.

An article in InformationWeek reports that40,000 ASU Students Leap to Google Apps; University Pays Zero. The ASU president, Michael Crow, wants to make IT the primary driver in his ambitious "New American University" project.Last October, ASU became the first large institution to deploy Google Apps, a comprehensive suite of productivity applications that includes e-mail, search, calendars, instant messaging, and even word processing and spreadsheets.I've tried them out, they work, nothing fancy but certainly good enough for college homework assignments.

Already 40,000 students and faculty have switched their e-mail to Google, while keeping their asu.edu designation. (out of 65,000 student population, which Mr. Crow is trying to raise to 90,000 students!)

E-mail is a thorn in the side of storage administrators. Being "semi-structured" repositories, they cannot just delete or move files around, as there is context between notes and their attachments, that shouldn't be broken. E-mail systems are often the fastest growing consumer of storage for many organizations.

Switching from maintaining their own mail servers to Google is saving ASU $500,000 US dollars alone, not including the administrator labor savings. Again, some corporations might feel their e-mail is too "secret" to be outsourced like this, but for college students who spend all their creative talent posting things on MySpace and YouTube, and faculty who spend their careers TRYING to get published, they have nothing to hide from the rest of the world. It makes perfect sense.

Best of all, Google isn't charging ASU anything for this service. Google is able to cover the costs from advertising revenue instead. I can think of a lot of companies that might want to advertise to a demographic of "40,000 students who are mostly 18-25 years old and all live in or near Tempe, AZ".

For about 25 years, movies were silent, actors acted, text was shown on the screen, and an organ or piano player added the musical score. My mother was a concert pianist, so I grew up listening to all kinds of piano music. Last weekend, while I was in Chicago for St. Patricks Day, we watched and listened to the dueling pianos at a bar called "Howl at the Moon". Those not familiar with this art form can watch this 1-minute video of Star Wars re-imagined as a Silent Movie.

About 80 years ago, "talkies" appeared. The sound was converted to a series of colors that were recorded as a separate strip on the film media itself, hence the name "soundtrack". When the movie ran, the colors would then be converted back to voice and music. While the live piano players were out of jobs, the move to sound created a whole new industry for foley artists, orchestras and composers.InformationWeek's Mitch Wagner explains in Something Will Be Lost thatgreat artists like Charlie Chaplin and Mary Pickford never completely made the transition to talkies.

Now the movie industry is changing again, this time from film to digital format. Thanks to digital, we can now see videos on the internet, such as this set of Impressive Palindromes parody of a Bob Dylan song.

While movies are digital when you rent them from the DVD store, download them on iTunes, or play them on YouTube, they are still mostly in analog format on 35mm or 70mm film stock when you see them on the big screen.

My first "digital projection" experience was the movie "Ice Age" shown in Denver, Colorado. The theatre owner came out to show us what film stock looks like, and then how small the DVD was that held the digital version. The theatre also showed previews of other movies first on film, then in digital, so that we could see the difference in quality.My second experience was "Star Wars: Attack of the Clones (episode II)", which I saw opening night at the Ziegfeld theatre in New York City. This was a huge theatre, and we had front row seats in the upper balcony.

Of course, the transition of film stock to digital projection is just one of the many trends resulting in the fast growth of computer IT storage. Documents transitioned from paper, to being scanned into digital format, to being created digitally using word processing software. Likewise, photographs went from film, to being scanned, to being captured with digital cameras.

As with talkies, history repeats itself; the transition to digital projection is not going smoothly.NPR's Laura Sydell reports thatDigital Projection in Theaters Slowed by Dispute. The dispute is between movie production companies and theatre owners. Currently, it is quite expensive to send out film stock to all the theatres, so the transition to digital will save the movie production companies lots of money. On the other hand, installing digital projection equipment will be costly for theatre owners. How the two groups will share the burdensome costs to convert this infrastructure is still under negotiation.

As a fan of going to the movies, I hope they resolve this dispute soon.

Last Friday,The "Greater IBM Connection" team held a "red carpet" event, showcasing the winners of the Second Life "machinima".It is best explained on the Linden Lab website:

Machinima is the art of making real movies in virtual worlds.

Movies made in Second Life use the world's building, scripting, and avatar customization tools, working in real-time collaboration with people around the globe. You can use Second Life as your own virtual back lot, soundstage, choreography studio, costume and prop repository, and special effects house.

"Do you know what I do?" Mr. Mondavi recalls Mr. Gallo asked him when they first met."Yes, you run the largest winery in the country," recalls Mr. Mondavi, then in his mid-20s."No," Ernest corrected him. "I go out and visit customers in stores."

Robert Smith (aka Radio Voom) reports on National Public Radio that Second Life is now being used for campaigning for political candidates. It used to be that political candidates took trains and buses across the country, meeting people, discussing their issues, and getting a feel for what is going on in the hearts and minds of their potential voters. With the development of TV and Radio, candidates traveled less, hoping to get their word out to people who would listen to them. Using Second Life and other social networking tools brings candidates back to having conversations with the people they hope to represent.

Of course, many of these candidates are old, and are learning internet social networking skills for the first time. John McCain, my senator from Arizona, is running for President at 70 years old! It's true that old dogs CAN learn new tricks.

IBM is investing heavily into Second Life, as are many other forward-thinking companies, to explore the age-old human need for connectedness, community and dialog. I've asked my team to all get their avatars up and running in Second Life. Granted there is a bit of a learning curve, but everybody handles change in different ways, some better than others.

Why are most of these guys (and girls) with over a billion US dollars in net worth still working? Perhaps because they embrace new ideas, and are on the thrill seeking side of humanity. I guess I am too. I'll be thrill-seeking in Chicago this weekend, celebrating St. Patrick's day.

On the news today, they mentioned it was "Happy Pi Day". Today is the 14th day of the 3rd month, and "pi" is about 3.14159, the ratio of the circumference of a circle to its diameter. So, in Tucson it is celebrated on 3/14, at 1:59pm MST.

The ratio has a lot to do with storage.

Tape wrapped around a hub. Tape is thin, but not completely, so wrapping hundreds of meters on tape results in a change in diameter of the spool. This impacts the rotational velocity needed to get the linear meters-per-second on the tape media consistent as the diameter changes when you wind down from a full spindle toward the hub. IBM has variable speed motors and other clever technologies to handle this adjustment.

Disks spin at consistent speeds, but tracks on the outside edge travel faster across the head than the inside tracks.Currently, the top speeds for disk are 15000 Revolutions per minute (RPM). As faster rotational speeds are investigated, the researchers find they need to make the diameters smaller to compensate.

The diameters of disks were based on "U", the unit height of standard 19" racks. A "U" is 1.75 inches, and standard floppy diskettes were 5.25 inch (3U) and 3.5 inch (2U). For those who have a difficult time remember how many inches a "U" is, it is the height of a standard two-by-four (2x4) piece of lumber.

The value of "pi" has been calculated to over a billion significant digits. Here is a cuteapplet to use if you ever need the value to any level of accuracy.

Yesterday, most of the USA moved its clocks forward an hour. Arizona and Hawaii don't bother, as there is plenty of daylight in both states. While it may seem that Arizonans are not "affected" by Daylight Saving Time (DST), we are, because we have to deal with the time zone offsets with those we talk to in other states. (Note: it is SAVING not SAVINGS, many people mistakenly say "Daylight Savings Time", which is incorrect).

Year round, Arizona is on Mountain Standard Time (MST), which is GMT-7. Figuring out what time Arizona can be remembered by a simple mnemonic:

In the winter time, Utah, Colorado, New Mexico, and Arizona are all on MST, so best American ski resorts are all on the same time zone. People who hop from one ski resort to another by helicopter don't have to reset their watches as they move into or out of Arizona.

In the summer time, Arizonans head to San Diego, Los Angeles or other parts of California, where it is not so hot. California is on PDT, which is the same as MST. People who hop from Arizona wineries and vineyards to those in California and Oregon can easily cross the Arizona-California border without having to reset our watches.

Those in Second Life may have noticed that "Second Life time" (SL time) shifted from PST to PDT. That is because their servers reside in San Francisco, California.

The blogosphere has quieted down a bit over the two papers on MTBF estimates for Disk Drive Modules (DDM).One article on SearchStorage.com by Arun Taneja asksIs RAID passé? Disk capacity is growing at a faster rate than DDM reliability. During the hours to rebuild a DDM, companies are at risk of additional failures that could require recovery from a copy, or result in data loss, depending on how well your Business Continuity (BC) plan is written and followed.

... The problem with that is that it's the DISK ARRAY that determines when a drive has failed an starts the rebuild process. That IS under the control of IBM, specifically the controller. But more importantly, it effects my risk of data loss.

As I see it, my risk of data loss with RAID-5 is influenced by two main factors. 1 - The drive replacement rate and 2 - The rebuild time (which to a great extent is a function of the drive size) both of which IBM has some control over.

So, I think that the question in my mind is, what's the tipping point? Where does the risk of using RAID-5 protection exceed what I'm willing to accept, and I need to move to some other protection mechanism like RAID-6? Is it when the rebuild times exceed 12 hours? 24 hours? 48 hours?

Also, I wonder why IBM isn't publishing some information to help me make these kinds of decisions?

Oh, dear - while Tony doesn’t seem to be parrying vigorously (as Seagate, Hitachi, and Chunk were doing), his contribution sounds more like IBM marketing than the kind of detailed, technical response one might have hoped for

... well, he *is* a manager, and a marketing one at that, so perhaps we shouldn’t expect more).

Both are fair comments. Disk arrays do run microcode to assist or perform the RAID function, detect failures and start the rebuild process, and so clever designs to support spare disks, process the rebuild quickly, and so on, can differentiate one vendor's offering from another.

On the issue of what does IBM provide to help its clients make the right decisions for their environments, Jon William Toigo at DrunkenData points his readers to IBM's Business Continuity Self-Assessment tool. In normal data center conditions, DDMs will fail, and a Business Continuity plan shouldbe written and developed to handle this fact. Using 2-site and 3-site mirroring, complemented with versions of tape backups, can help address some of these concerns and mitigate some of the risks involved with using disk systems.

For those who want a more technical answer, IBM has just published a series of IBM Redbooks.

Each client's situation is different, so no simple answer is possible. However, IBM does have a lot of experience in this area, and would be glad to help you write or update your existing Business Continuity plan.

IBM beat HP both in 4Q06, as well as 2006 full year.You can read more about it from Gartner Dataquest report “Market Share: Disk Array Storage, All Regions, All Countries, 1Q05-4Q06" on their website. (Note: non-IBMers might need an account with Gartner to access this, not sure)

The focus was on external controller-based disk, not external controller-less SCSI/SAS disk, not disk arrays posing as virtual tape libraries, nor any disk sold inside HP, Sun, IBM or Dell servers. This is to compare with disk-only vendors such as EMC and HDS. The revenues reflect hardware only, including hardware-related parts of financial leases and managed services. Revenues from optional priced software features such as multi-pathing drivers, management software, or advanced copy services were excluded.I discussed these types of analyst reports back in blog post last September: Space Race Heats Up.

These marketshare numbers are based on revenues, not units or terabytes. When a box gets sold, the revenue was counted toward the vendor that sold it, not the manufacturer that built it. In this last report:

When Dell sells an EMC box, it gets counted as Dell. When Fujitsu Siemens sells an EMC box, it gets counted as "Other".

When HP sells an HDS box, it gets counted as HP. When Sun sells the HDS box, it gets counted as Sun.

When IBM sells its System Storage N series (from the OEM agreement with NetApp), it gets counted as IBM. Both IBM and NetApp experienced growth in the NAS/unified storage arena.

It's still cold here in the Washington DC area, but at least good news like this helps warm me up!

Well, this week I am in Maryland, just outside of Washington DC. It's a bit cold here.

Robin Harris over at StorageMojo put out this Open Letter to Seagate, Hitachi GST, EMC, HP, NetApp, IBM and Sun about the results of two academic papers, one from Google, and another from Carnegie Mellon University (CMU). The papers imply that the disk drive module (DDM) manufacturers have perhaps misrepresented their reliability estimates, and asks major vendors to respond. So far, NetAppand EMC have responded.

I will not bother to re-iterate or repeat what others have said already, but make just a few points. Robin, you are free to consider this "my" official response if you like to post it on your blog, or point to mine, whatever is easier for you. Given that IBM no longer manufacturers the DDMs we use inside our disk systems, there may not be any reason for a more formal response.

Coke and Pepsi buy sugar, Nutrasweet and Splenda from the same sources

Somehow, this doesn't surprise anyone. Coke and Pepsi don't own their own sugar cane fields, and even their bottlers are separate companies. Their job is to assemble the components using super-secret recipes to make something that tastes good.

IBM, EMC and NetApp don't make DDMs that are mentioned in either academic study. Different IBM storage systems uses one or more of the following DDM suppliers:

In the past, corporations like IBM was very "vertically-integrated", making every component of every system delivered.IBM was the first to bring disk systems to market, and led the major enhancements that exist in nearly all disk drives manufactured today. Today, however, our value-add is to take standard components, and use our super-secret recipe to make something that provides unique value to the marketplace. Not surprisingly, EMC, HP, Sun and NetApp also don't make their own DDMs. Hitachi is perhaps the last major disk systems vendor that also has a DDM manufacturing division.

So, my point is that disk systems are the next layer up. Everyone knows that individual components fail. Unlike CPUs or Memory, disks actually have moving parts, so you would expect them to fail more often compared to just "chips".

If you don't feel the MTBF or AFR estimates posted by these suppliers are valid, go after them, not the disk systems vendors that use their supplies. While IBM does qualify DDM suppliers for each purpose, we are basically purchasing them from the same major vendors as all of our competitors. I suspect you won't get much more than the responses you posted from Seagate and HGST.

American car owners replace their cars every 59 months

According to a frequently cited auto market research firm, the average time before the original owner transfers their vehicle -- purchased or leased -- is currently 59 months.Both studies mention that customers have a different "definition" of failure than manufacturers, and often replace the drives before they are completely kaput. The same is true for cars. Americans give various reasons why they trade in their less-than-five-year cars for newer models. Disk technologies advance at a faster pace, so it makes sense to change drives for other business reasons, for speed and capacity improvements, lower power consumption, and so on.

The CMU study indicated that 43 percent of drives were replaced before they were completely dead.So, if General Motors estimated their cars lasted 9 years, and Toyota estimated 11 years, people still replace them sooner, for other reasons.

At IBM, we remind people that "data outlives the media". True for disk, and true for tape. Neither is "permanent storage", but rather a temporary resting point until the data is transferred to the next media. For this reason, IBM is focused on solutions and disk systems that plan for this inevitable migration process. IBM System Storage SAN Volume Controller is able to move active data from one disk system to another; IBM Tivoli Storage Manager is able to move backup copies from one tape to another; and IBM System Storage DR550 is able to move archive copies from disk and tape to newer disk and tape.

If you had only one car, then having that one and only vehicle die could be quite disrupting. However, companies that have fleet cars, like Hertz Car Rentals, don't wait for their cars to completely stop running either, they replace them well before that happens. For a large company with a large fleet of cars, regularly scheduled replacement is just part of doing business.

This brings us to the subject of RAID. No question that RAID 5 provides better reliability than having just a bunch of disks (JBOD). Certainly, three copies of data across separate disks, a variation of RAID 1, will provide even more protection, but for a price.

Robin mentions the "Auto-correlation" effect. Disk failures bunch up, so one recent failure might mean another DDM, somewhere in the environment, will probably fail soon also. For it to make a difference, it would (a) have to be a DDM in the same RAID 5 rank, and (b) have to occur during the time the first drive is being rebuilt to a spare volume.

The human body replaces skin cells every day

So there are individual DDMs, manufactured by the suppliers above; disk systems, manufactured by IBM and others, and then your entire IT infrastructure. Beyond the disk system, you probably have redundant fabrics, clustered servers and multiple data paths, because eventually hardware fails.

People might realize that the human body replaces skin cells every day. Other cells are replaced frequently, within seven days, and others less frequently, taking a year or so to be replaced. I'm over 40 years old, but most of my cells are less than 9 years old. This is possible because information, data in the form of DNA, is moved from old cells to new cells, keeping the infrastructure (my body) alive.

Our clients should approach this in a more holistic view. You will replace disks in less than 3-5 years. While tape cartridges can retain their data for 20 years, most people change their tape drives every 7-9 years, and so tape data needs to be moved from old to new cartridges. Focus on your information, not individual DDMs.

What does this mean for DDM failures. When it happens, the disk system re-routes requests to a spare disk, rebuilding the data from RAID 5 parity, giving storage admins time to replace the failed unit. During the few hours this process takes place, you are either taking a backup, or crossing your fingers.Note: for RAID5 the time to rebuild is proportional to the number of disks in the rank, so smaller ranks can be rebuilt faster than larger ranks. To make matters worse, the slower RPM speeds and higher capacities of ATA disks means that the rebuild process could take longer than smaller capacity, higher speed FC/SCSI disk.

According to the Google study, a large portion of the DDM replacements had no SMART errors to warn that it was going to happen. To protect your infrastructure, you need to make sure you have current backups of all your data. IBM TotalStorage Productivity Center can help identify all the data that is "at risk", those files that have no backup, no copy, and no current backup since the file was most recently changed. A well-run shop keeps their "at risk" files below 3 percent.

So, where does that leave us?

ATA drives are probably as reliable as FC/SCSI disk. Customers should chose which to use based on performance and workload characteristics. FC/SCSI drives are more expensive because they are designed to run at faster speeds, required by some enterprises for some workloads. IBM offers both, and has tools to help estimate which products are the best match to your requirements.

RAID 5 is just one of the many choices of trade-offs between cost and protection of data. For some data, JBOD might be enough. For other data that is more mission critical, you might choose keeping two or three copies. Data protection is more than just using RAID, you need to also consider point-in-time copies, synchronous or asynchronous disk mirroring, continuous data protection (CDP), and backup to tape media. IBM can help show you how.

Disk systems, and IT environments in general, are higher-level concepts to transcend the failures of individual components. DDM components will fail. Cache memory will fail. CPUs will fail. Choose a disk systems vendor that combines technologies in unique and innovative ways that take these possibilities into account, designed for no single point of failure, and no single point of repair.

So, Robin, from IBM's perspective, our hands are clean. Thank you for bringing this to our attention and for giving me the opportunity to highlight IBM's superiority at the systems level.